The expense of transporting and setting up drilling rigs at new drill sites can be time consuming and costly. Transporting the equipment for drilling oil and gas wells is often costly because such equipment is heavy and bulky. For example, modular drill rigs often include a mast of over a hundred feet when fully erected, a drilling floor, and a substructure to support the drilling floor and mast. The substructure raises the drilling floor off of the ground at a sufficient height to accommodate equipment connected to the well bore, such as a blowout preventer. The blowout preventer often includes a series of high pressure valves that prevent oil, gas, or water from exiting the well bore when the drill string encounters high pressure regions while drilling through various subterranean formations. Blowout preventers are often ten feet to thirty in height and weigh several tens of thousand pounds.
Transporting the rig generally includes disassembling the components of the drill rig into manageable loads that meet government regulations for transport on truck beds and trailers. At the new drill site, the rigs are assembled in place before the well head equipment is positioned in place. Thus, the blowout preventer is positioned under the drill floor after the drill rig is at least partially assembled. Often, during assembly of the drill rig, hoists and other equipment for handling the blowout preventer into place are transported independent of the substructure and reattached to portions of the drill rig.
One type of rig with a system to position a blowout preventer is disclosed in U.S. Pat. No. 7,389,820 issued to Mark A. Day. In this reference, a blowout preventer system includes a mast functionally connected to a frame assembly and a carriage functionally connected to the mast. The carriage is adapted to carry and support a blowout preventer in a manner such that the blowout preventer may be moved along an angular path and along a plurality of linear paths. The system may further include a mechanism for rotating the blowout preventer along a first rotational path. The system may further include a mechanism for rotating the blowout preventer along a second rotational path.
Other types of systems are described in U.S. Pat. No. 7,628,225 issued to Inge Petersson, et al, and U.S. Pat. No. 6,161,358 issued to David A. Mochizuki, et al. All of these documents are herein incorporated by reference for all that they contain.